FAAM non-core instrument measuring dew point or frost point by a chilled mirror hygrometer.

The Buck CR2 is a chilled mirror hygrometer for use in cloud-free air - it optically monitors the temperature of a mirror when liquid water or ice begins to condense. Air is drawn through the instrument through an aft facing inlet, located 1.8 m aft of the nose, outside the 99% free-stream boundary layer.

The data frequency is measured in 1Hz and be found in this frequency in both the 32Hz and 1Hz data files.

Parameters in the data files are: VMR_CR2 (Water vapour volume mixing ratio measured by the Buck CR2, ppmv),VMR_C_U(Uncertainty estimate for water vapour volume mixing ratio measured by the Buck CR2,ppmv),TDEW_CR2(Mirror Temperature measured by the Buck CR2 Hygrometer, K),TDEW_C_U(Uncertainty estimate for Buck CR2 Mirror Temperature, K)